Electrical coil and method of winding same.



E. A. DE WOLF.

ELECTRICAL COIL AND METHOD OF WLNDING SAME.

APPLICATION FILED MAY 28, 1915.

1,204,749. Patented Nov. 14, 1916.

2 SHEETS-SHEET E. A. DE WOLF.

ELECTRICAL COIL AND METHOD OF WINDING SAME.

APPLICATION FILED MAY 28. 1915.

1,204,749 Patented Nov. 14, 1916.

2 $HEETSSHEET 2- UNITED STATES PATENT OFFICE.

ERNEST A. DE WOLF, OF MANSFIELD, MASSACHUSETTS, ASSIGNOR, BY MESNEASSIGN- MENTS, TO UNIVERSAL WINDING COMPANY, OF BOSTON, MASSACHUSETTS, ACOB- PORATION OF MASSACHUSETTS.

Specification of Letters Patent.

Patented Nov. 14, 1916.

Application filed May 28, 1915. Serial No. 81,032.

To all whom it may concern:

Be it known that I, Ennnsr A. DE VVoLF,

a citizen of the United States, residing at Mansfield. in the county ofBristol, State of Massachusetts, have invented certain new and usefulImprovements in Electrical Coils and Methods of Winding Same, of whichthe following is a specification.

My invention relates to coils for electrical purposes, such as magnet,solenoid, relay, armature, field, reactance and resistance coils, andconsists particularly of an improved method of winding the same.

The object of my improvement is to produce a coil with the layers ofwindings so disposed as to give increased electrical efiiciency within aminimum space; to provide for greater stability and prevent displacementof the windings; to reduce the amount of insulation required; toeconomize in the copper wire or other conducting-material employed; toincrease the number of turns within given dimensions; to prevent arcingor short-circuiting between the individual turns and between the layersof windings; to relieve the potential strains between different portionsof the windings; and to otherwise enhance the efiiciency of the coilboth mechanically and electrically, all as set forth more particularlyhereinafter.

The invention is fully described in the following specification,illustrated by the accompanying drawings, in which like referencecharacters designate like parts.

In the drawings:-Figure 1 is a view of one form of my improved coilshowing it as partly completed; Fig. 2. a sectional view illustratingthe arrangement and disposition of the layers of windings in this formof coil; Fig. 3, a sectional view of a modified form of coil in whichthe same principles of winding are applied in a slightly differentmanner; and Fig. 4, a part-sectional view of this same form of coilshowing a different method of applying insulation between the layers ofwindmgs.

Referring first to Figs. 1 and 2, it will be observed that my new methodof winding the coil contemplates the novel arrange ment of the layersthereof in conoidal or partly conoidal planes, lying in superimposedrelation and stepped one in advance of another longitudinally of theaxis of the coil. In other words, instead of winding the coil in theusual manner with the turns of wire or other conducting-materialdisposed in cylindrical planes superimposed one directly over the otherand concentrically with respect to their common axis, the layers ofwindings are caused to advance along the axis so that they overlap atthe ends and assume a conical form. As the winding continues with thelayers progressing axially of the coil, step by step, in conical planes,after the coil reaches a predetermined diameter it grows by longitudinalextension only and this growth can be carried as far as desired withoutincreasing the diameter or the length of the turns in each layer. Inthis way each succeeding layer is composed of the same number of turnscomprising the same length of wire as in each preceding layer and alldisposed in uniform relation to the axis of the coil.

Figs. 3 and 4 illustrate the most uniform distribution of the turns ofwire in the layers of the coil for in this application of my improvedsystem the first or starting layers are laid on a tapered butt orfoundation cone formed as a part of the core of l the coil. With thisarrangement all of the layers are in the form of true cones having thesame angle of inclination to the axis of the coil, and hence there willbe a uniform length of wire in each layer. In Figs. 1 and 2 thefoundation for the ultimate, conical layers is shown as built up by thewire itself which is laid first in a cylindrical layer with the next andsubsequent layers overlapping at their forward ends so that graduallythe Winding assumes a conical form which is continued in the main bodyof the coil. the same with all of the layers of the same length andoverlapping at their ends so that the coil grows by longitudinalextension with the layers forming an obliquely and progressivelylaminated structure resembling somewhat the scale formation on the legs.of birds. This method of winding in progressive, coniform layers is ofcourse old as applied to the textile art, being extensively used inwinding cops and With either method the principle is bobbins of fillingthread or yarn. As applied to the winding of electrical coils, however,I believe its use to be novel and its advantages are numerous andmanifest as will be explained hereinafter.

Specifically, my new system of winding coils according to the presentimprovement comprises certain steps as follows: Referring particularlyto Fig. 2, when the coil is to be built up on a cylindrical core such asthe tube or shell S, which may be of paper, fiber or of metal adapted toserve as an armature, the first layer of the windings is laid incylindrical form concentric with the axis of the core. The length of thelayers, or in other words, the length of traverse of the wire-windings,is established in accordance with the number of turns required perlayer, and this determines the ultimate diameter of the coil. That is tosay, if the windings are deposited on the core or tube S with arelatively long traverse the layers will build up to a greater diameterbefore assuming the full,- conical formation {than if the traverse ismade shorter. It has before been explained that, the coil reaches itsmaximum diameter when the windings commence to lay in completely conicalplanes and therefore it will now be obvious that the longer the traversethe greater the diameter of the windings, and hence the ultimatedimensions of the coil can be determined and regulated as desired bysimply adjusting the length of the traverse at the start of the coil.The length of traverse of the windings in each layer also determines theangle of inclination of the layers, that is, their degree of taper withrespect to the axis of the coil. For this reason it is necessary toestablish primarily a length of traverse which will give the properpitch or taper to the plane of the subsequent layers without tending tocause the?" wire-windings to slip out of place. This point is a matterwhich is determined by experiment in accordance with the size ordiameter of the wire being wound and other conditions, it being obviousthat a comparatively fine wire can be wound more conveniently and theturns will stay in place better on a steeper taper than will arelatively coarse, heavy wire.

In Fig. 2 I have shown the layers of windings as wound with a length oftraverse which gives a taper adapted for most varieties of wire employedfor electrical purposes, and the resultant coil is of proportionssuitable for various uses. In this figure the black sections W representthe layers of wire or other conducting-material in the coil while thewhite sections X indicate the insulating-material disposed between thewire layers. No attempt is here made to illustrate the individual turnsof wire in the different layers as separate and distinct from eachother, but in Figs. 3 and 4 the relation between the adjacent turnsorconvolutions of the wire is shown more graphi- .layers of thewire-windings, and any suitable method may be adopted for this purpose.For instance, the well known practice of insertingstrips of paperbetween the layers can be employed, and, as shown in Fig. 2, thesestrips or sheets X are preferably of slightly greater length than thewire layers in order that they may overlap and protect the end turns ofthe wire. In Fig. 2 I have shown first a strip or sheet of paper it laidaround the tube S and on top of this the first layer to of wire iswound. On top of this another strip of paper w is laid and around thisthe second layer of wire to is wound. This process continues with eachsucceeding layer of windings stepped slightly forward of the precedinglayer and advanced along the axis of the coil. The forward, overlappingportions of the layers will thus be caused to build up in conical form,as shown in Fig. 2, until a point is reached where the last layer 10 isdisplaced along the coil entirely beyond the last end of the first layerw. At this juncture the windings in the layer "w will be laid wholly ina conical plane and thereafter all of the layers will assume this formwhile being deposited one over another and slightly in ice advance ofeach other longitudinally of the coil. The coil now ceases to increasein diameter, but continues to grow through longitudinal extension andthe winding can be carried on indefinitely to attain any desired numberof turns or in accordance with the length required.

In the foregoing description I have explained the simplest manner ofbuilding the coil with sheets of insulation inserted between its layers.The preferred method of producing coils of this form is, however, by acomparatively new system which has certain advantages particularlyapplicable to the present invention. This consists in winding cottonyarn or other attenuated textile material of an insulating characterinto the coil simultaneously with the winding of the wire or otherconductor. This new method of building electrical coils is known as theLeeson-Universal system, and is described in detail in United StatesPatent No. 1,080,830, granted to Max Helm Dec. 9, 1913. Briefly, itconsists in winding the strands of yarn or other textile materialcrosswise of the turns of wire to weave them in and out through the wirelayers and thus link the wire-windings together to bind them in place.This method of building the coil is illustrated in Fig. l which showsthe turns of wire to laid in the conical layers Z with the usual close,spool-wind, while the strands of yarn 3 are laid in open helices in thecross-wind generally known as the Universal system. The wire is laidwith a relatively slow traverse to deposit the turns in close relation,while the yarn is wound with a much faster traverse so that theconvolutions cross eachother at sharp angles. The yarn-windings liediagonally of the wire turns and, weaving in and out through the layers,form a mechanical binder which holds the wire in place and serves as areinforcing medium for the whole coil. This feature is particularlyimportant with the form of coil herein disclosed because, as will berecognized, it is more diiiicult to wind on a tapered surface than on acylindrical one. l/Vhen winding in a conical plane the turns of wirewill have a tendency to slide down the taper and slip out of place, andwith the present system of tying the layers in position suchdisplacement can be effectually prevented. Furthermore, theyarn-windings not only serve as a binding and reinforcing means for thewire-windings but they also build up insulation between the layers ofthe coil. That is to say, the frequent crossing and recrossing' of thestrands of yarn results in the formation of a protecting covering overeach layer of wire and while this does not completely inclose thewire-windings the yarn builds up more thickly at the ends of the wirelayers where the potential difference in voltage between layers isgreatest and therefore the primary insulation of the wire is reinforcedand strengthened at these vulnerable points.

It is the preferred practice to wind the yarn or otherinsulating-material with a slightly longer traverse than that of thewire and in this way the ends of the wire layers are more thoroughlyprotected and reinforced. In fact, the overlapping of the yarn-windingsat the smaller diameter of the wire layers, that is at the nose of thewinding, acts to build up a sort of abutment-ring or collar which holdseach layer from slipping down outof place. The overlapping of theyarn-layers at the opposite or butt end of the wire-layers serves tocover the exposed turns of the wire as shown at b in Fig. 1, and afterthe last layer of the coil is finished this can also be protected bycontinuing the yarn-winding to complete a final covering layer. In thisway the whole coil can be completely armored by a covering ofinsulating-material without requiring a separate operation of taping 1t,and finally the coil is immersed in shellac, cement, paraflin, liquidbakelite or other coating material which solidifies into a hard shell.The windings of yarn which intervene between the wire-windings absorbthe cement or other coating medium in such a manner that the whole massof the coil is thoroughly impregnated and its parts amalgamated so thata particularly staunch and stable structure is secured.

In Figs. 3 and 4 I have illustrated the core C on which the coil iswound as formed with a conical head or butt B. This provides that thefirst windings of wire can be disposed in conical planes so that all thelayers will have the same number of turns with a uniform length of wirein each layer and all of the layers having the same relation to the axisof the coil. In Fig. 1 the form of the coil is represented by dashlines, and the first few layers are illustrated with the turns of wireshown in section. The first two wire layers are represented at t and t,and the overlapping yarn layers are indicated at y, 3

Fig. 4 shows a similar form of coil with the wire layers designated 0,c, 0 etc., and with sheets of insulating-material 7), 72 72 etc.,inserted therebetween. The last layer of wire 0 is shown as not quitecompleted, the wire w being illustrated as winding back toward the baseend of the coil.

As previously stated it has been demon strated that many advantages,both electrical and mechanical, result from winding the coil with itsturns or convolutions disposed in coniform layers. In the first place,all of the layers can be composed of the same number of turns wound froma uniform length of wire, thus providing for greater uniformity in theresistance factor for all parts of the coil. Another important advantageis that the coil can be wound with a large number of turns withoutbuilding it up to an excessive diameter, and hence there will be a Veryconsiderable saving in wire. Furthermore, the length of the layers ofwindings can be maintained at the minimum while producing a coil of anylength required. In this way the mean length of turn can be kept at aminimum so that the potential strain between the end turns of the layerswill be greatly reduced. In addition, the distance from the first layerof the coil to the last layer is greatly extended and thus the potentialstress between different sections of the coil is minimized.

Heretofore, when it has been required to produce a coil with a largenumber of turns or convolutions of wire it has been necessary to buildit up in sections which are wound separately and then strung togetherand when placed end for end must be thoroughly insulated one fromanother. This requires a relatively large amount of insulating-nmterialwhich is not only expensive but also takes up valuable space. With theimproved form of coil herein disclosed this separating-insulation can bedispensed with so that its cost is saved and a considerable economy inspace effected, thus providing for more turns of wire in a coil of givendimensions or, putting it another way, the same number of turns can bewound into a coiloccupying much less space. It will also be obvious thatthe cost of producing a composite coil with the sections wound.separately and afterward joined together will be much greater. onaccount of the extra operations required, than with the present methodof winding the coil as a unit completed in one operation.

Still other advantages in the present method of building the coil resultfrom stepping the layers progressively forward, one in advance ofanother. A much more stable and staunch structure is produced in thisway because there will be no tendency for the end turns of the wire tofall down over the ends of the coil or to be otherwise displaced. Thestepped relation of the ends of the layers alsorelieves the potentialstrain between the end windings and provides against arcing orshort-circuiting at these points. For this reason the insulatingcovering of the wire is less liable to be ruptured and less extrainsulation is therefore required at the ends of the layers. It willreadily be seen that my improved coil is much stronger in structure thanthe usual form of coil wound with superimposed cylindrical layers. Noheads or flanges are required to hold the windings in place and theoverlapping, conical layers act as mutual reinforcement, one foranother, much like the buttresses of a building. Besides these physicaladvantages above pointed out there are also certain electricaladvantages accruing from the conoidal form of the lay ers in my improvedcoil. For instance, the turns of the wire in each layer are broughtcloser to the path of greatest density of the magnetic flux, that isnearer to the axis of the coil. It is well known that the electricdensity on a cylinder with rounded ends is greater at the ends than inthe center, and on a cone the density increases as we approach the apex.For this reason the tendency of the current passing through the layersof windings will be to approach the axial center of the, coil so thatits magnetic efliciency will be .much higher than that of the ordinarycylindrically-wound coil. Other advantages of this novel method ofproducing electrical coils will occur to those versed in the art andwill become apparent from a practical demonstration of its use.

Certain modifications might be made in the form and dimensions of thecoil and in the method of producing it without departing from the mainprinciple of the im- .what I claim is 1. An improved coil for electricalpurposes composed of a plurality of overlying layers of convolutionsdisposed in frustoconical planes, with all of the layers having auniform diameter at the baseand vertex.

2.- An improved coil for electrical purposes composed of a plurality ofsuperimposed layers having the turns therein disposed in conical planesadvancing progressively along a common axis, with all of the layers ofuniform length.

3. An improved coil for electrical purposes composed of overlappinglayers of uniform length stepped progressively in advance of each otheralong a common axis with the turns therein disposed in conical planes.

4. An improved electrical coil composed of a. plurality of superimposedlayers of convolutions disposed in conical planes about a common axiswith the turns in each layer wound from a uniform'length of wire.

5. An improved electrical coil composed .of a plurality of overlyinglayers of convolutions disposed in conical planes with all layerscomprising a uniform number of turns wound from equal lengths of wire.

6. An improved electrical coil composed of a plurality of superimposedlayers of convolutions disposed about a common axis with each succeedinglayer stepped progressively in advance of the beginning of eachpreceding layer, and with all of the layers of uniform length.

7. An improved electrical coil composed of a series of coniform layersof convolutions advancing progressively along .a common axis with thebase ends of the layers forming the cylindrical periphery of the coil,and with all of the layers of uniform length.

diameter of the axial core on which the coil is wound and at the otherend with the maximum diameter of the coil.

10. An improved electrical coil composed of a plurality of superimposed.layers advancing progressively along a cylindrical core and overlappingeach other at their forward ends to build up a structure having opposedfrusto-conically shaped ends.

11. An improved electrical coil shaped with oppositely-tapered orconical ends formed by winding the turns of the coil in superimposed,overlapping layers stepped progressively forward along a common axis tobuild the ultimate layers with the convolutions disposed in conicalplanes.

12. An improved electrical coil composed of a series of overlappinglayers of wire turns of uniform length advancing progressively along acommon axis with crosswindings of insulating-material disposeddiagonally of the wire-windings and woven in and out through the wirelayers to reinforce the structure and secure the Wire turns in place.

13. An improved electrical coil composed of a series of coniform layersof wire con- 'volutions of uniform length disposed about a common axiswith windings of insulatingmaterial laid cross-wise of the wire-windingsand Woven in and out through the layers to reinforce the structure andbind the wire turns in place.

14. An improved method of producing electrical coils consisting inwinding the wire or other conductor in conical planes advancingprogressively along a common axis with all of the layers of uniformlength angs. overlapping each other at their forward en t 15. Animproved method of producing electrical coils consisting in winding thewire or other conductor in layers of uniform length steppedprogressively in advance of each other along a common axis so that thelayers eventually assume a conical form.

16.An improved method of producing electrical coils consisting inwinding the wire or other conductor in superimposed, conical layers ofuniform length advancing progressively along a common axis to build up astructure having a cylindrical periphery terminating in acomically-tapered end.

17. An improved method of producing electrical coils consisting inwinding conducting-material in superimposed layers of uniform lengthstepped progressively forward along a common axis to overlap each otherat their forward ends and simultaneously winding insulating-materialdiagonally of the wire-windings to weave it through the layers toreinforce the structure and bind the wire turns in place.

18. An improved method of producing electrical coils consisting inwinding the wire or other conductor in superimposed layers of uniformlength stepped progres sively in advance of each other along the axis ofthe coil and simultaneously winding strands of insulating-materialdiagonally of the wire-windings with a longer traverse than that of thewire to bind the wire turns in place and secure them at the ends of thelayers.

In testimony whereof I afiix my signature in presence of two Witnesses.

ERNEST A. DE WOLF.

l/Vitnesses: 4

CHARLES C. HAona'rY, GEORGE B. PARK.

